/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.mpp.aggregation.timerangeiterator;

import org.apache.iotdb.db.utils.datastructure.TimeSelector;
import org.apache.iotdb.tsfile.read.common.TimeRange;

public class PreAggrWindowWithNaturalMonthIterator implements ITimeRangeIterator {

    private static final int HEAP_MAX_SIZE = 100;

    private final boolean isAscending;
    private final boolean leftCRightO;
    private final TimeSelector timeBoundaryHeap;

    private final AggrWindowIterator aggrWindowIterator;
    private long curStartTimeForIterator;

    private long lastEndTime;
    private TimeRange curTimeRange;
    private boolean hasCachedTimeRange;

    public PreAggrWindowWithNaturalMonthIterator(
            long startTime,
            long endTime,
            long interval,
            long slidingStep,
            boolean isAscending,
            boolean isSlidingStepByMonth,
            boolean isIntervalByMonth,
            boolean leftCRightO) {
        this.isAscending = isAscending;
        this.timeBoundaryHeap = new TimeSelector(HEAP_MAX_SIZE, isAscending);
        this.aggrWindowIterator =
                new AggrWindowIterator(
                        startTime,
                        endTime,
                        interval,
                        slidingStep,
                        isAscending,
                        isSlidingStepByMonth,
                        isIntervalByMonth,
                        leftCRightO);
        this.leftCRightO = leftCRightO;
        initHeap();
    }

    @Override
    public TimeRange getFirstTimeRange() {
        long retStartTime = timeBoundaryHeap.pollFirst();
        lastEndTime = timeBoundaryHeap.first();
        return new TimeRange(retStartTime, lastEndTime);
    }

    @Override
    public boolean hasNextTimeRange() {
        if (hasCachedTimeRange) {
            return true;
        }
        if (curTimeRange == null) {
            curTimeRange = getFirstTimeRange();
            hasCachedTimeRange = true;
            return true;
        }

        if (lastEndTime >= curStartTimeForIterator) {
            tryToExpandHeap();
        }
        if (timeBoundaryHeap.isEmpty()) {
            return false;
        }
        long retStartTime = timeBoundaryHeap.pollFirst();
        if (retStartTime >= curStartTimeForIterator) {
            tryToExpandHeap();
        }
        if (timeBoundaryHeap.isEmpty()) {
            return false;
        }
        lastEndTime = timeBoundaryHeap.first();
        curTimeRange = new TimeRange(retStartTime, lastEndTime);
        hasCachedTimeRange = true;
        return true;
    }

    @Override
    public TimeRange nextTimeRange() {
        if (hasCachedTimeRange || hasNextTimeRange()) {
            hasCachedTimeRange = false;
            return getFinalTimeRange(curTimeRange, leftCRightO);
        }
        return null;
    }

    private void initHeap() {
        TimeRange firstTimeRange = aggrWindowIterator.nextTimeRange();
        if (leftCRightO) {
            timeBoundaryHeap.add(firstTimeRange.getMin());
            timeBoundaryHeap.add(firstTimeRange.getMax() + 1);
            curStartTimeForIterator = firstTimeRange.getMin();
        } else {
            timeBoundaryHeap.add(firstTimeRange.getMin() - 1);
            timeBoundaryHeap.add(firstTimeRange.getMax());
            curStartTimeForIterator = firstTimeRange.getMin() - 1;
        }
        tryToExpandHeap();
    }

    private void tryToExpandHeap() {
        TimeRange timeRangeToExpand = null;
        while (aggrWindowIterator.hasNextTimeRange() && timeBoundaryHeap.size() < HEAP_MAX_SIZE) {
            timeRangeToExpand = aggrWindowIterator.nextTimeRange();
            if (leftCRightO) {
                timeBoundaryHeap.add(timeRangeToExpand.getMin());
                timeBoundaryHeap.add(timeRangeToExpand.getMax() + 1);
                curStartTimeForIterator = timeRangeToExpand.getMin();
            } else {
                timeBoundaryHeap.add(timeRangeToExpand.getMin() - 1);
                timeBoundaryHeap.add(timeRangeToExpand.getMax());
                curStartTimeForIterator = timeRangeToExpand.getMin() - 1;
            }
        }
    }

    @Override
    public boolean isAscending() {
        return isAscending;
    }

    @Override
    public long currentOutputTime() {
        return leftCRightO ? curTimeRange.getMin() : curTimeRange.getMax();
    }

    @Override
    public long getTotalIntervalNum() {
        long tmpInterval = 0;
        while (hasNextTimeRange()) {
            tmpInterval++;
            nextTimeRange();
        }

        curTimeRange = null;
        timeBoundaryHeap.clear();
        aggrWindowIterator.reset();
        initHeap();

        return tmpInterval;
    }
}
